This invention relates to a refrigerant system that incorporates an economizer heat exchanger and liquid-suction heat exchanger within a single common heat exchanger construction.
Refrigerant systems are utilized in applications to change the temperature and humidity or otherwise condition the environment. In a standard refrigerant system, a compressor delivers a compressed refrigerant to an outdoor heat exchanger, known as a condenser. From the condenser, the refrigerant passes through an expansion device, and then to an indoor heat exchanger, known as an evaporator. In the evaporator, moisture may be removed from the air, and the temperature of air blown over the evaporator coil is lowered. From the evaporator, the refrigerant returns to the compressor. Of course, basic refrigerant systems are utilized in combination with many configuration variations and optional features. However, the above provides a brief understanding of the fundamental concept.
An enhancement technique known as an economizer cycle has been utilized in refrigerant systems. The economizer circuit increases the capacity and efficiency of a refrigerant system. When the economizer circuit is functioning, a refrigerant is tapped from a main liquid refrigerant line at the position downstream of the condenser. This tapped refrigerant is expanded to a lower pressure and temperature and then passed through a heat exchanger where it exchanges heat to cool the main refrigerant flow. This tapped refrigerant is then returned to the compressor through the intermediate compression port. The main refrigerant flow having been cooled in the economizer heat exchanger has a greater cooling capacity when it reaches the evaporator.
Another way to increase refrigerant system performance is to use a liquid-suction heat exchanger. In such an arrangement, refrigerant downstream of the evaporator is passed through a heat exchanger where it subcools liquid refrigerant flowing from the condenser to the expansion device. This scheme provides additional cooling capacity when the refrigerant reaches the evaporator, but at the expense of having higher temperature and lower density refrigerant reaching the compressor.
The use of the economizer heat exchanger option would provide the most benefits under some operating conditions, while the use of the liquid-suction heat exchanger would provide the most benefits under other operating conditions. In the past, the designer had to choose between using either one option or the other. Providing both options has been expensive and somewhat cumbersome as two separate heat exchangers were required.